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What is the Large Hadron Collider?

Journey inside the LHC, the largest and most powerful particle accelerator ever built.

The LHC is the largest and most powerful particle accelerator ever built. It took international teams numbering in the thousands to design, construct and operate the 27 km collider and its four giant particle detectors and was designed and built on the back of decades’ worth of expertise, technology and machinery – both from CERN’s own past and from the wider international physics community. A decade in the construction, the LHC stands as a monument to human ingenuity and ambition.

The LHC tunnel
The LHC tunnel. © CERN

What is a collider?

In some ways, a collider is a simple and rather brutal device. They take tiny particles, accelerate them to tremendous speeds, and smash them into each other. The reason is not to break particles apart to see what they are made of, but to create altogether new particles from the energy of the collisions.

In this sense colliders aren’t 'atom-smashers', but particle factories, creating new and exotic matter from pure energy. By studying these new particles, physicists learn more about the physical laws that govern our universe at the most fundamental level.

Colliders vary in design. Some, like enormous rifles, fire particles at each other in straight lines, while others whirl them round a ring. The type of particle selected for colliding also differs, ranging from everyday electrons to more exotic particles of antimatter.

CERN’s Large Hadron Collider (LHC) is the largest and most powerful particle collider ever built. Housed in a 27-km tunnel beneath the Swiss-French border, it fires two beams of hadrons around and around in a circle before colliding them into each other. A hadron is a category of particle, and includes the stuff that makes up the atomic nucleus: neutrons and protons. The LHC mostly uses protons, but occasionally picks much larger projectiles, such as lead nuclei.

Machinery inside LHC tunnel © CERN

The LHC’s line of radio-frequency accelerating cavities.

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